The present invention relates generally to locks for the doors of a vehicle. In particular, it is related to locks for, cars, which locks are provided with an electrical signalling circuit for indicating to the driver whether the door of the car is open, only partially closed, or correctly fully closed. Still more in particular, the invention relates to a lock as defined above and comprising a supporting body, a movable member which is held by said body and is able to occupy a first position wherein the lock is closed, a second position wherein the lock is partially closed, and a third position wherein the lock is open.
Electrical warning systems, e.g. for cars, have in principle already been proposed. Thus, U.S. Pat. No. 3,771,154 (Takei) discloses a warning system and apparatus including a device for receiving a signal indicative of an abnormal condition. A magnetic switch cn be used for sensing the existence of abnormal conditions. The warning system circuit is enabled when a magnet is moved away from the magnetic switch, i.e. when a door is opened to which the magnet is attached. The use of the system in a car is disclosed to be possible but is not described.
U.S. Pat. No. 3,697,943 proposes an installation for indicating the closed condition of vehicle doors based upon the status of a vacuum source.
In U.S. Pat. Nos. 3,426,166 and 3,539,741(Voland), magnetically operated or activated door switches, but not closure indicating devices, are described.
The location of overhead doors can be detected, according U.S. Pat. No. 3,975,723 (Bowling et al.) by reed switches which are under the influence of a (feeble) permanent magnetic field and a stronger, movable field.
None of these patents discloses or suggests the invention which is to be described now in detail.